Another day, another revelation of an ethically questionable business practice by Uber. This time The Information reports that Uber secretly tracked Lyft drivers using an internal software program it dubbed Hell.

Hell not only let Uber see how many Lyft drivers were available for rides and what their prices were, but also figure out which ones were double-dipping by driving for Uber, too.

Hell originated after Uber created fake rider accounts on Lyft and used software to trick Lyft’s system into thinking those riders were in certain locations. This allowed Uber to see the eight closest available Lyft drivers to each fake rider.

Then Uber executives realized that Lyft had assigned a numerical user ID to each of its drivers. This bonanza allowed them to start long-term tracking of Lyft drivers and deduce who also drove for Uber. Once Uber knew when and where they tended to log onto Lyft, the company was able to offer drivers incentives–including financial bonuses–created to convince them to use only Uber.

The Information talked to lawyers from firms who have represented Uber in other cases who said Uber can potentially face civil legal claims related to its use of Hell. These include breach of contract, unfair business practices, stealing trade secrets and violating the Computer Fraud and Abuse Act. A Uber spokesman told The Information that the company won’t publicly discuss its internal processes, while Lyft said “We are in a competitive industry. However, if true, these allegations are very concerning.”

According to The Information’s sources, Uber stopped using Hell in early 2016, around the time Lyft closed a $1 billion funding round. Only a few people at Uber knew about Hell, including Kalanick, several other executives and data scientists.